Propeller



T. A1 DICKS June '14,. 1932.

PROPELLER Filed Dec. 2, 1950 Sheets-Sheet Patented June 14, 1932- UNITED STATES PATENT OFFICE THOMAS A. mcxs, or PITTSBURGH, rENNsYLvA IA, ASSIGNOR To PITTSBURGH scnnw & BOLT CORPORATION. OF'PITTsBU GH, PENNSYLVANIA, A CORPORATION or PENN- SY LVANIA ,raornntna l edge of the propeller blade which tends to resist the forward movement of the propeller and which decreases the operating efiiciency of the propeller.

This vacuum not only resists the forward movement of the plane but also causes air to rush from the high pressure area along the leading edge of the blade into the vacuum with such force that 'a terrific noise is created which makes airplane travel uncomfortable and in time impairs the hearing of the effect of the vacuum.

those riding in the plane.

It is an object of this invention to expel air from the propeller into the vacuum formed along the trailing edge to neutralize Another object of this invention is to provide a propeller which can be rotated at high speed with comparatively little noise.

' 'A still further object of this invention is to provide a propeller having greater efliciency and considerably less resultant noise.

These and other objects which may be ap-- parent to those skilled in this particular art are accomplished by means of this invention, one embodiment of which is described in the following specification and illustrated .in the accompanying drawings, wherein:

Figure 1 is a front elevation, partially in section, of a hub having the propeller blades tially broken away;

Fig. 2 is a VIEW insection taken at 90 to ig. 3 is a top plan view of Figure 2 pars i t F1 4 is a front elevation of a propeller blade;- 1'

Fi 5 is a view-of the blade shown in Fig.

4, an at right angles thereto; and

Fig. 6 is a view of the blade shown in-Figure 5,"showing the hub and shank thereof in section.

Propellers have been made heretofore 'in; p

which provision was made for reducing the vaeuum formed along the trailing edge of the blades. These propellers differ from my invention in that air is forced into those blades under pressure, the hub having openings facing in the direction of travel of the plane for that purpose of forcing air into the blades. Theair in the blades is discharged intothe vacuum through openings whose total area is less than the area of the openings through which the air is forced into the blade so that a high velocity will be imparted to the air forced out of the blades along the trailing edge.

Inmy improved propeller the air in the hollow blades is drawn into the vacuum through slots along the trailing edge ofthe blade partly by the, action of the air passing over the slot which sets up a Venturi effect .along the trailing edge of the blades and partly by the action of centrifugal force. As the air is expelled from the blade, a low pressure area is created in the blade and more air is drawn into the blade throughan opening in the hub which faces in the direction of rotation of the hub and not in the direction of travel of the plane, so that air is not forced solid type hub which is mounted on a motor shaft The hu is provided withsockets 11 and 12,

radially disposed to the airis thereof, in which {kpot shown) in the usual manner.

the shanks of hollow tubular propeller blades 13 and 14 are mounted. The bladesare held in the sockets by the usual clamp on the outer end of the socket, as indicated at 15and 16,

end by the usual locking" meansextending through oppositely disposed openings in the wall of the socket and the' propeller blade, as indicated at 16. .[Eaehs'ocketpfl the hub is provided -with a' poit or" openingi'fl ad- 1- jacenttlie base thereof and'on that surface of the socket which faces in the direction of rotation of the propeller.

The direction of rotation of the propeller is indicated by the arrow of Figure 1. A portion of the shank of each blade is cut away, as at 18, to register with the port 17, so that air may enter into the blade through the hub. Each blade is also provided with slots 19 and 20 along the edge thereof.

The slots 20 at the tip of the blade are substantially semi-circular in shape. It is to be understood that the slots 19 and 20 are cut along the trailing edge of the blade and on one surface only of the blade.

lVhen the propeller is rotating, a low pressure area is created along the trailing edge thereof into which the air in the-hollow blades is expelled through the slots 19 and 20, partially by centrifugal force and partially by a Venturi effect, set up by the air passing over the said slots. The expelling of the air from the blades lowers the pressure therein and air rushes into the blade from the high pressure area at the hub through the port 17.

Expelling the air circulating through the blade from the hub to the trailing edge thereof into the low pressure area formed by the rotation of the propeller tends to raise the pressure along the trailing edge and thereby effectively neutralize the partial vacuum and increase the efficiency of the plane, since a low pressure area along the trailing edge of the propeller tends to resist forward movement thereof.

This neutralizing of the vacuum raises the pressure along the trailing edge of the blades considerably and as a result the force of the air rushing into the vacuum from the high pressure area is greatly reduced and consequently the noise created by the rushing of the air into the vacuum is reduced at least 50%. The circulating of air through the blade from the hub to the trailing edge of the blade thus effectively deadens the noise created by the propeller and removes one of the greatest drawbacks to air travel.

The difference between the pressure at the leading edge of the propeller and the trailing edge depends on the speed at which the propeller is rotating and, as is readily seen from the above description, the amount of air expelled into the low pressure area along the trailing edge is likewise dependent on the speed of rotation, since the forces expelling the air from the blade, that is the centrifugal force and the suction set up by the air passing over the slots, are greatest at the highest speed of the propeller. Thus the low pressure area is effectively neutralized regardless of the speed at which the propeller is rotating.

lVhile I have described one embodiment of my invention. it is apparent that certain changes, omissions and substitutions may be made therein without departing from the spirit of this invention, or the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent is:

1. In combination, a hub having radially disposed sockets provided with ports facing in the direction of rotation, and a detachable hollow propeller blade adapted to be received in each of said sockets and having a portion of the shank thereof cut away and registering with said port, and having slots along the trailing edge thereof for creating a low pressure area in said blade on rotation thereof so as to cause air to flow from the hub to the trailing edge of said propeller.

2. In combination, a hub having radially disposed sockets and a detachable hollow propeller blade for each of said sockets, each of said sockets having a port at the base thereof facing in the direction of rotation of said hub and each blade having a portion of the shank thereof cut away and registering with the port in said socket so that air may be drawn into the blade, and having slots along the trailing edge at the outer end thereof through which the air is expelled.

3. In a propeller the combination of a hub having radially extending sockets, each socket having a port therein, a hollow propeller blade disposed in each of said sockets and having a recess in the shank thereof registering with the port in said socket, and means for setting up a low pressure area in each of said blades on rotation of said propeller for circulating air through said blades to decrease the vacuum formed at the trailing edges of said propeller and deadenthe noise thereof.

4. In a propeller the combination of a hollow hub, radially extending sockets on said hub each having an opening therein adjacent the base thereof and facing in the direction of rotation of said hub and a detachable hollow propeller blade disposed in each of said sockets and having a recess in the shank thereof registering with the opening in the socket, and means for drawing air through said registering opening and recess and for expelling the same along the trailing edge of said blade so as to neutralize the vacuum and reduce the noise set up by the whirling of said propeller.

5. In combination, a hub having radially disposed sockets each of which has a port formed therein adjacent the base thereof, and

a detachable hollow propeller blade for each of said sockets having a portion of the shank thereof cut away and registering with the port in said socket for admitting air to said blade and having openings along the trailing edge thereof for creating a low pressure area in said blade as the same is rotating so as to cause air to be drawn through said hub into said blade and expelled through the openings along the trailingedge thereof for deadening the noise of said'propeller.

6. In a propeller, the combination of a hub having radially disposed sockets, each of which has a port therein and a detachable hollow propeller ets, having a portion of the shank thereof cut away and registering with said port and having slots along the trailing edge thereof for creating a low pressure area in each of said blades on rotation of said propeller so as to cause air to flow from the hub tothe trailing edge of said blades.

7. In a propeller the combination of a hub having radially-extending sockets each of which is provided with a port adjacent the base thereof and facing in the direction of rotation of said hub, a detachable hollow propeller blade for each of said sockets having the portion of the shank adjacent the port cut away to form an air passage into said blade, and means for creating a low pressure area in said blade when the propeller is rotating so as to circulate air through said blade and deaden the noise created by the whirling of said propeller.

In testimony whereof, I have-hereunto subscribed my name this 29th day of November,

' THOMAS A. DIOKS.

blade for each of said sock- 

